Generally, there are at least three different types of golf balls that are currently commercially available. These are one-piece balls, multi-piece solid balls having two or more solid pieces or components, and wound balls.
The one-piece ball typically is formed from a solid mass of moldable material which has been cured to develop the necessary degree of hardness. The one-piece ball possesses no significant difference in composition between the interior and exterior of the ball. These balls do not have an enclosing cover. They are utilized frequently as range balls or practice balls. One piece balls are described, for example, in U.S. Pat. No. 3,313,545; U.S. Pat. No. 3,373,123; and U.S. Pat. No. 3,384,612.
Conventional multi-piece solid golf balls, on the other hand, include a solid resilient center or core comprising a single or multiple layer of similar or different types of materials. The core is enclosed with a single or multi-layer covering of protective material.
The one-piece golf ball and the solid core for a multi-piece solid (non-wound) ball frequently are formed from a combination of materials such as polybutadiene and other rubbers cross-linked with zinc diacrylate (ZDA) or zinc dimethacrylate (ZDMA), and optionally containing fillers and curing agents. The cores are molded under high pressure and temperature to provide a ball of suitable hardness and resilience. For multi-piece non-wound golf balls, the cover typically contains a substantial quantity of thermoplastic or thermoset materials that impart toughness and cut resistance to the covers while also providing good playability and distance characteristics. Examples of suitable cover materials include ionomer resins, polyurethanes, polyisoprenes, and nylons, among others.
The wound ball is frequently referred to as a “three-piece” ball since it is produced by winding vulcanized rubber thread under tension around a solid or semi-solid center to form a wound core. The wound core is thereafter enclosed in a single or multi-layer covering of tough protective material. For many years the wound ball satisfied the standards of the U.S.G.A. and was desired by many skilled, low handicap golfers.
The three piece wound ball typically has a cover comprising balata, ionomer or polyurethane like materials, which is relatively soft and flexible. Upon impact, it compresses against the surface of the club producing high spin. Consequently, the soft and flexible covers along with wound cores provide an experienced golfer with the ability to apply a spin to control the ball in flight in order to produce a draw or a fade, or a backspin which causes the ball to “bite” or stop abruptly on contact with the green. Moreover, the cover produces a soft “feel” to the low handicap player. Such playability properties of workability, feel, etc., are particularly important in short iron play and at low swing speeds and are exploited significantly by highly skilled players.
However, a three-piece wound ball has several disadvantages. For example, a soft wound (three-piece) ball is not well suited for use by the less skilled and/or medium to high handicap golfer who cannot intentionally control the spin of the ball. In this regard, the unintentional application of side spin by a less skilled golfer produces hooking or slicing. The side spin reduces the golfer's control over the ball as well as reduces travel distance. Consequently, the impact of an unintentional side spin often produces the addition of unwanted strokes to the golfer's game.
The above described golf balls are produced by various golf ball manufacturers to be generally uniform in consistency. In essence the different layers are designed to be uniform in composition and the covers or centers are essentially perfectly centered. The center of gravity (“COG”) of these commercial balls is very desirably at the center point of the ball.
Unlike the conventional balls briefly described above, the balls of the present invention are not uniform in consistency. The balls of the invention have been specifically designed to produce a controlled weight distribution about a designated spin axis. In this regard, the subject golf balls of the invention utilize different density regions or gradients positioned at various locations within one or more layers of the balls. It has been found that this selectively controlled weight distribution imparts a spin stabilization effect about the ball's spin axis. Such a selected weight distribution also corrects the undesired side spin that is produced when the ball is incorrectly struck or mishit with a golf club.
In this regard, when a ball is properly struck, the ball will rise in flight towards the intended direction of travel. This is due to the transformation of forces from the club to the ball and the lift produced by the ball which is back spinning in the air.
Specifically, after being properly struck, the ball will spin about an axis horizontal to the ground (“horizontal axis”) such that the bottom of the ball moves in the direction of flight and the top moves opposite to the direction of travel. This results in the ball back spinning in the air in the direction of travel about an axis of rotation or spin axis. As the ball spins (i.e. backspins) in flight, the ball lifts into the air. The addition of dimples or surface depressions in the ball surface further increase the lifting forces by creating localized areas of turbulence.
However, when a ball is improperly struck (i.e. the club face is not traveling in the same direction that it is desired for the ball to take), a side spin is also imparted on the ball. When this occurs, the ball is forced to one side or another of a desired flight path resulting in a curved flight known as “hook” or “slice.” Such a curved flight pattern is generally undesirable by the average golfer.
Accordingly, the present invention is directed to improved golf ball components and golf balls employing the same, which have a weight distribution that produces a preferred spin axis. The preferred spin axis is perpendicular to a gyroscopic center plane and corrects side spin imparted by striking the ball with an open or closed club face. These and other objects and features of the invention will be apparent from the following summary of the invention, description of the preferred embodiments, the drawings and from the claims.